This invention relates to a proportioning valve apparatus located in the outlet port of a master cylinder for controlling the communication of pressurized brake fluid supplied to the rear wheels of a vehicle.
U.S. Pat. No. 3,686,864 discloses a brake system having a master cylinder with a failure warning switch, a proportioning valve and a metering valve incorporated therein. The output of the master cylinder is connected to front disc brakes through the metering valve and to the rear drum brakes through the proportioning valve to provide substantially uniform braking between the disc and drum brakes. In the event of a brake failure in the front wheel brake system, a shuttle valve moves a first lever to activate the failure warning switch and a second lever which opens a by-pass to allow fluid under pressure to be communicated to the rear wheels without passing through the proportioning valve. This type of lever arrangement, while functioning adequately in engineering laboratory testing has not been completely successfully adapted into production manufacturing techniques since a manual adjustment of the levers is required on each unit constructed to assure proper functioning between the interconnected warning switch and proportioning valve.